Shape-effect composite armor system

ABSTRACT

An armor system for protecting an object from the impact of a projectile. A core layer of hardened metal or ceramic balls supported in a softer material, wherein the surfaces of the balls are in contact with adjacent ball surfaces and the sizes of the balls are selected with respect to the anticipated shape of the projectile being armored against. Inward and outward facing reinforced layers at the surfaces of the core layer. The reinforced layers including a resin base and fibers therein. A backing plate may back the core layer on the rear surface.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.61/208,563, filed on Feb. 26, 2009, incorporated herein by reference.

BACKGROUND OF THE INVENTION

There is a pressing need for lightweight armor systems to protectmilitary and civilian vehicles and equipment. Existing armor systems areoften heavy and expensive, and often rely on Rolled Homogeneous Armor(RHA) plates which are heavy and difficult to fabricate into shapedarmor systems.

A breakthrough in armor systems would be a system that is lighter thanconventional armor, while also being formable into complex shapes andbeing producible at a reasonable cost.

SUMMARY OF THE INVENTION

Disclosed herein is a composite armor system that preferably combinesthe hardness of steel with the toughness of a plastic composite, with aweight reduction believed to be 30-40% below RHA and produced at reducedfabrication costs.

The armor takes advantage of an effect that a shaped surface of hardmaterial has on a projectile that strikes the surface. The incomingprojectile interacts with the armor in several basic ways. First, theprojectile is physically blunted and deformed by a high-speedinteraction with the hard, curved outer surface of the armor. Second,the projectile is deflected from its original path, thereby transferringa portion of its forward momentum into the plane of the armor. Third,the energy of the projectile is spread over a larger surface area alongthe direction of the entire travel of the projectile. Lastly, the armorsystem spreads the projectile's energy in the plane of the armor as theprojectile is trapped between adjacent curved surfaces.

The armor system is a composite structure comprised of at least one andpreferably two reinforced outer layers wherein each reinforced layer isat one side of and two of the reinforced layers are on opposite sides ofand surround one or more hardened and correspondingly shaped innerlayers (called core layers). The reinforced layers are of a resinstrengthened by included fibers. The core layer is also of a resin whichincludes preferably one layer that contains an array of small size ballsall touching adjacent balls in the array. Each ball is sized to aboutthe size of a projectile to be armored against. The balls are of metalor a ceramic. They are of a material such that they have a surfacehardness at least as hard as or harder than the impact surface of theprojectile expected to strike the armor.

An array of reinforcing wires connect the projectile facing outer layerto the core layer.

The basic armor system described herein is preferably a three-layerarmor. But, it can be expanded with additional core and/or reinforcedlayers in various arrangements to address increased threat levels, andprovide greater strength or penetration resistance or protect againstother unique projectiles.

Other objects and features of the present invention will become apparentfrom the following description of the invention which refers to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary and cut away perspective view of a firstembodiment of an armor system embodying the invention.

FIG. 2 is a fragmentary cut away view of a second embodiment; and

FIG. 3 illustrates a shaped armor.

DESCRIPTION OF PREFERRED EMBODIMENTS

In the cutaway view of an armor system in FIG. 1, the system includesseveral layers. There is a core layer 13. There are shown preferablytwo, opposite reinforcing layers at the opposite surfaces of the corelayer, including outer layer 11, which will face outwardly from theobject on which the armor is placed and toward an incoming projectile,and inwardly facing inner layer 15, which will face inwardly toward theobject that is being protected by the armor. In order that the objectbeing protected itself provides at least one support for the armor, theinner reinforced layer 15, to the extent possible, is shaped to theshape of the surface of the object on which the layer 15 is applied (seeFIG. 3), so that the object helps the armor resist any projectile andthereby protects the object that is armored. The other layers will havea shape that corresponds to the shape of the inner layer.

The reinforced layers 11, 15 that are placed at the front and rear ofthe armor system are comprised of a known thermoplastic resin, which isa bonding resin, described below. The resin is highly-loaded, at about70 to 80% by volume of added reinforcement material, comprised of Eglass fibers of relatively long length, e.g., 3 to 6 inches. Use of thisfiber length may preclude the use of standard injection molding of thelayers, so the reinforced layers are compression molded using heat toreflow the thermoplastic Bonding Resin. The fiber reinforcement may alsobe stronger S-glass fibers, Kevlar, other specialty fibers, carbonfibers, nanotubes or other materials of this type. The fibers arerandomly arranged in three dimensions in their respective layers toprevent delamination of the layers or of the armor upon projectileimpact, as delamination typically occurs with mat-based systems.However, in some situations it may nonetheless be desirable to use amat-based reinforcement material. That material is also cheaper due tothe reduced pre-processing needed to fabricate the reinforcement fibers.The fiber systems are broken down into small groups of fibers or evensingle fibers to maximize the interaction of the fibers with the bondingresin.

One example of the bonding resin in the reinforced layers is preferablyfinely-powdered, preferably having a particle size of 0.002 inches to0.010 inches and preferably comprised of a polycarbonate, which isselected for its toughness and thermal formability. It is alternativelypossible to use thin sheets of the desired thermoplastic to form thecomposite structure. The fine powder assures a high level of surfacecontact with the fiber reinforcements. The use of a thermoplastic allowsforming the armor in flat sheets and then re-forming the sheets (seeFIG. 3) into more complex shapes through re-heating and pressing them.Very complex shapes can also be formed in a final or near-final stage.This enables shaping the armor to the object armored.

Alternative bonding resins can be selected to vary the properties of thereinforced layers and the armor system. These resins include otherthermoplastic resins as well as thermosetting materials such as epoxies.The bonding resin may be solid and homogenous through its thickness, orit may be varied by the addition of microspheres or foaming agents,primarily used to reduce weight in part or all of the layer's thickness.These modifications can be made in some or all reinforced layers and inany combination.

The thickness of each reinforced layer may be between 0.10 inches and0.6 inches. The thickness may be varied within or outside of this rangedependent on the threat level of projectiles which may impact the armor.The outer and inner reinforced layers may also be of differentrespective thicknesses to optimize the design for a particular use.

In the first embodiment of FIG. 1, the core layer 13 is generally flator planar as are the reinforced layers 11, 15. In the alternative thirdembodiment of FIG. 3, the core layer 33 is curved in shape to rest onand conform to the surface 38 being armored, for example. The innerreinforced layer has a curved surface 37 to conform to the curvedsurface 38 to be armored. The inner and outer reinforced layers 35 and31 are correspondingly curved or profiled on their inward facingsurfaces to fit to the core layer and make a firm composite armorarrangement. Shown in broken lines in FIG. 3 is curved area 38 of anobject, like the surface of a vehicle shown in broken lines, and thearmor is correspondingly curved or shaped to the surface there armored.

The core layer 13, 23, 33 (of FIGS. 1, 2 and 3) is comprised of hardmaterial, preferably e.g., ⅜″ diameter surface-hardened steel balls 16,26. For best performance, the balls 16, 26 are in a single layer and arethere in a tightly-arrayed design. For example, the array of balls is sotight that the outer surface of each ball is normally preferably intouching contact with the outer surface of adjacent balls in the corelayer and three adjacent balls define and surround an open area, intowhich, for example, a below described reinforcement 14 may extend.

Each ball 16 is preferably of a size on the same order of magnitude asthe projectile against which the armor protects. Very small ballsrelative to a projectile to be protected against may act as ahomogeneous material and may be simply displaced by the projectile. Verylarge balls are heavy and may make the armor unnecessarily heavy due toadded thickness of the core layer due to the ball size. If the balls arevery large, they may approach acting as a flat plate and then they wouldnot interact with the projectile.

The balls are preferably of a material and are so constructed as to havea surface hardness of at least about the same hardness as the impactsurface of a projectile against which the armor protects, or a greaterhardness. Such balls may be of a hardened steel, a hardened ceramic,another hardened metal, including aluminum. In particular, the surfaceof the ball is hard.

Other designs for the core layer 3 could use different-sized balls,hollow steel balls to reduce weight, through-hardened balls, solid orhollow balls of other hard materials such as ceramics. Use of the ballsallows for simple post-forming of the thermoplastic-based reinforcedlayers since the balls are not formed into a rigid sheet, like a plateof steel.

A key element is a discontinuity between the hardness of the center corelayer and the relative softness of the front or outward reinforcedlayer. Hard spheres in a matrix of hard material in the core layer donot present this discontinuity to the projectile.

The composite armor structure is then reinforced in a directionperpendicular to the plane of the layers and at least in part in thedirection of a path of a projectile, called axial reinforcement,preferably by incorporation of short length, high-strength steel wires14 with a preferred diameter that is preferably less than or equal tothe space defined between and surrounded by each array of three touchingballs in the layer 13. This avoids wires forcing contacting balls apart,which would disrupt a pattern of balls in layer 13 and could preventsome balls touching neighboring balls in a pattern with a preferredabout 1 inch spacing between wires. This spacing can be varied dependingupon the projectile expected to be stopped. The individual spaced apartaxial reinforcement elements extend at least through the reinforcedlayer that may be impacted by the projectile and optionally, butpreferably, extend further partially at least through the adjacent corelayer. Without such reinforcement perpendicular to the surface of thearmor, the system may delaminate upon impact. Because the reinforcedlayers may be mats of woven glass, the reinforcement wires are bent overat their ends or have end fixtures that reduce the chance thereinforcement wires will move out of the plastic material of the armorlayers.

Other materials and systems can be used to provide the placement of theballs and the axial reinforcement of the layers. The balls can bemechanically held in place during a portion of the fabrication of thecenter core layer. The axial reinforcement can be provided by using thesame fiber material as is used in the reinforced layers or using adifferent material, such as those mentioned as candidate reinforcementsabove.

An alternative embodiment of the armor is shown in FIG. 2. Except asdescribed here, it may be the same as the first embodiment. The core andreinforced layers 23 and 21, 25 may be the same as in FIG. 1 and havethe same reference numbers raised by 10. The balls 26 in the core layer23 are ground flat on their rear facing surfaces 27 toward the object tobe armored. The balls may be ground to a depth of approximately 30% ofthe diameter of the ball. Grinding more off the balls, e.g., 50% maycause the balls to ride up on neighboring balls instead of pressingagainst them. This removal of part of the balls reduces the arealdensity of the core layer and therefore of the armor. The balls 26 aresupported by a thin steel back plate 22. The plate 22 further spreadsthe energy from a projectile impact onto a larger area of the rear orinner reinforcement layer 21, increasing the stopping power of thearmor. The make-up and properties of the back plate can be optimized fora specific projectile and armor application.

The core layer 13, 23, 33 can also be formed as a unified structureeither by removal of material e.g., EDM of a hardened steel plate, or bydeposition of material e.g., powder metallurgy or plating processes, orby forming e.g., forging and then hardening of steel plates. Thissimplifies fabrication of the core by trading off flexibility andpost-formability.

It is envisioned that this armor system can be manufactured in largeplates in a vertically-oriented process. The first stage of manufactureforms the core structure. Simple optical inspection is possible sincethe balls are easily visible.

The second stage applies the reinforcement layers 11 and 15 to the frontand back of the core layer 13 to the desired thicknesses, then appliesthe axial reinforcements 14. A final inspection may be made with anon-destructive method such as ultrasonic or x-ray to detect any gaps ormissing balls in the core layer or voids in the reinforcement layers.

Sheets of the armor can be made as wide and long as fabricationequipment permits, typically on the order of 5 to 10 feet wide and 10 to20 feet long. Post-forming can be done with thermoplastic based systemsto achieve curved surfaces as long as the above described inherentstructure of the layers is preserved. Complex shapes with tight radiicould be formed in the net-shape with dedicated tooling.

Prototypes of the armor system have been designed, built, and tested.During observations by the inventors hereof, the armor systems hereofhave demonstrated excellent stopping power as well as excellent arealdensity values, making this a viable and attractive product for thedefense and commercial armor markets.

Although the present invention has been described in relation toparticular embodiments thereof, many other variations and modificationsand other uses will become apparent to those skilled in the art. It ispreferred, therefore, that the present invention be limited not by thespecific disclosure herein, but only by the appended claims.

1. Armor system for application to an object to be armored, wherein thearmor system is intended to stop passage of a projectile, the armorsystem comprising: a core layer comprising: a tightly arrayed pattern ofa layer of hardened balls in the core layer, wherein the balls have adiameter of about one to two times the diameter of a projectile to bearmored against and the balls have a surface hardness of about the samehardness or harder than an impact surface of the projectile to bearmored against; a material much softer than the balls disposed at thecore layer and surrounding the balls for holding the balls in a layoutin the core layer; the core layer having opposite surfaces; a reinforcedlayer at least one of the surfaces of the core layer for reinforcing thearmor.
 2. The armor system of claim 1, wherein the reinforced layer ison one of the opposite surfaces of the core layer which is outward ofthe object to be armored and faces toward the projectile to be armoredagainst.
 3. The armor system of claim 2, further comprising anotherreinforced layer on the opposite surface of the core layer inward towardthe object to be armored also for reinforcing the armor.
 4. The armorsystem of claim 3, further comprising a backing plate between the corelayer and the reinforced layer at the surface of the core layer awayfrom the projectile, wherein the backing plate is configured to preventthe balls moving out of the core layer.
 5. The armor system of claim 3,wherein the inward reinforced layer has a shape selected to correspondto a shape of a surface of an object being armored by the armor system.6. The armor system of claim 3, wherein the reinforced layer comprisesfibers in a random array and supported in a resin.
 7. The armor systemof claim 1, wherein the balls in the core layer are hardened steelballs.
 8. The armor system of claim 1, wherein the balls in the corelayer are hardened ceramic balls.
 9. The armor system of claim 1,wherein each ball has an outer surface and the array of balls is tightsuch that the outer surface of each ball is in touching contact with theouter surfaces of adjacent balls in the core layer.
 10. The armor systemof claim 1, wherein the armor is of reduced areal density by havingremoved from the balls a fraction of the material of each of the balls,wherein the removal comprises at least one of a flat formed on a rearsurface of the ball facing away from the side thereof to be impacted bythe projectile and a hollowed area formed in a rear center of the ball.11. The armor system of claim 1, further comprising a plurality of axialreinforcements extending across at least the reinforced layer to beimpacted by the projectile and optionally extending into the core layer.12. The armor system of claim 11, wherein each ball has an outer surfaceand the array of balls is tight such that the outer surface of each ballis in touching contact with the outer surfaces of adjacent balls in thecore layer.
 13. The armor system of claim 12, further comprising axialreinforcements located to extend into the core layer into spacessurrounded by adjacent contacting balls.
 14. The armor system of claim11, wherein the axial reinforcements are at approximately 1 inch centersapart.
 15. The armor system of claim 11, wherein the axialreinforcements are of a material of high strength.
 16. The armor systemof claim 15, wherein the reinforcements are of steel wire.
 17. The armorsystem of claim 1, wherein the core layer is so configured and of suchmaterial as to be bonded to a polymer based composite armor.
 18. Thearmor system of claim 1, wherein the at least one reinforced layer ispositioned on a rear surface of the core layer away from impact from theprojectile and backing the core layer, and the at least onereinforcement layer is configured, shaped and positioned to restrictmovement of individual ones of the balls rearwardly, with respect to therear surface of the core layer, as a result of impact by the projectileon the armor system from a direction of an opposite front surface of thecore layer.
 19. The armor system of claim 1, wherein the material in thecore layer surrounding the balls therein comprises a reinforcedthermoset or a thermoplastic material.
 20. The armor system of claim 17,wherein the material surrounding the balls in the core layer comprises afiberglass reinforced epoxy, or a fiberglass reinforced polycarbonate,or a low-density metal or aluminum.